Most of the conventional MEMS devices or motion sensors have been composed of a MEMS die and an ASIC die, and then a wire bonding package technology is used to bond these two dies together. FIG. 1A shows a schematic view of an exemplary wire bonding package embodiment. As shown in FIG. 1A, a MEMS die 102 and an ASIC die 103 are attached to a lead frame 101. Bond wires 104 are then used to connect MEMS die 102, ASIC die 103 and lead frame 101. A CAP 105 is then attached to MEMS die 102. The drawbacks are that package processes are often complicated because wafer probing is needed on both MEMS and ASIC dies separately. Since the signals from MEMS dies are very small, the wafer probing on it is quite a challenge. Because of the complexity of two-die package, the final device tends to become large in package size in planar X-Y dimension, as shown in FIG. 1A. FIG. 1B shows another schematic view of an exemplary wire bonding package embodiment. As shown in FIG. 1B, a MEMS die 102 stacked on an ASIC die 103 on lead frame 101 with a CAP 105 on MEMS die 102 will result in a large size in vertical Z-dimension. By using the conventional methods to form MEMS devices, wafer level flip chip technology cannot be used in fabricating MEMS devices.
Several semi CMOS MEMS types of process using single-chip technology to manufacture MEMS motion sensor have been proposed. However, the drawbacks of these methods are that Flip Chip bumping process cannot be performed and thus neither wafer-level package (WLP) nor chip scale package (CSP) is possible. Also, the cap wafer needs to have a plurality of open holes 106 to allow for pad opening for wire bonding, i.e., wire bond window (WBW), to ASIC die 103, as shown in FIG. 1C.
It is therefore imperative to devise a novel structure for single-chip MEMS motion sensor to overcome the aforementioned drawbacks and to meet the present demands of increasingly wide range of applications.